Damped light valve



July 19, 1932. o. 0. CECCARINI DAMPED LIGHT VALVE Filed Jan. 7. 1931 f 30" a3 B J ,3; v z ii V Inventor dttamey:

Patented July 19, 1932 UNITED STATES PATENT orrics OLINDO 0. 030cm 0] BEVERLY HILLS, CALIFORNIA, ABSIGNOlB. '10 METRO- maxim-imam CORPORATION, 01' GULVEB CITY. CALIFORNIA, A CORPORATION 01' NEW YORK nmaii Liam: vaLvn Application Med January 7, 1981. Serial Io. 507,194.

This invention relates to an apparatus for modulating light for the purpose of producing sound records.

A light modulating device of this general character is generally referred to as a light valve and will be thus identified hereinafter.

This invention. particularly relates to a light valve capable of modulating light with greater accuracy so that the sound records obtained by the use of the improved 1i ht valve are substantially free of resonant reuencies and transient frequencies having t eir origin in the resonant requency of the light valve itself. I

The light valve of this invention is articularly adapted to be used in the recor ing of sounds for subsequent reproduction 111 proper timed relation with the reproduction of scenes such as motion pictures.

The equipment ordinarily employed in sound recording comprises a plurality of microphones or sound collecting means which are connected to a mixer controlling the gain of amplifiers for the recording machmes. The current from the microphones then passes through an amplifier, one or more equalizers and an attenuator and then into the recording machines. The recording machines (when photo raphic records of the sounds are being ma e) generally include a constant source of light and a light valve throughwhich the signal currents rom the amplifiers are passed.

A lens system is ordinarily employed, such lens system being adapted to focus the imageof the slit made by the light valve on a continuously moving .film.

The hght valve of the prior art generally comprised a 100 of metallic tape suspended in a plane at rig t angles to a magnetic field.

- The amplified voice currents passing through such tape when the electromagnet (of which the light valve assembly is a part) is energized from a battery or other source of direct current cause the two sections of the ribbon or loop to open or close in accordance with the current alternations, thereby increasing or decreasing the width of the aperture through which the light is bein passed. The volume of light thus modi ed produces a variable density record on the moving film, the record generally assuming the form of striations.

The metallic loop described hereinabove is under tension and the natural frequency of of the power required to fully modulate the light valve at any other frequency. Furthermore, transientsare capable of excitin the valve at the resonant frequency very rea ily and therefore sound records produced with ordinary light valves are unsatisfactory because of t e almost constant presence of vibrations or sounds other than the, true sounds which it is desired to record.

Again, light valves of the character used heretofore not only vibrate in a plane transverse to the magnetic field but in addition the ribbons appear to oscillate and tip, very often hitting the pole pieces, thereby destroying the true naturalness of the recorded sounds.

An object of this invention is to disclose and provide a light valve which will not respond to transient impulses.

Another object is to disclose and provide a light modulating device which is of simple construction which has a relatively high natural resonance period and which will not respond to transient impulses.

A still further'object is to disclose and provide'av light modulating device in which the movable light modulating element vibrates in a predetermined plane and is not readily dislodged therefrom.

An object of this invention is to disclose N and provide a light valve which employs but in transient vibrations while permitting spole ieces 2 and 3.

necte ci atory currents to energize and actuate the valve.

These and other objects, uses and advan- 3 tages of the invention will become apparent to those skilled in the art from the followin detailed description of one preferred orm thereof. In describing the invention, reference will 2 behad to the appended drawing, in which:

Figure 1 is a plan view of the improved light valve assem ly.

Figure 2 is an enlarged transverse section taken along the plane 2-2 indicated in Flgi5 ure 1.

' 35 pieces 2 and 3. Bridges 6 and 7 may be carried by the armature plate 1. The metallic .tape 8 may be connected to an' anchor lpost 9 extending from av suitable bracket or older 10 carried by the armature plate'l, the an- .9 chor post 9 being electrically connected to a terminal post 11 leading to the source of os- 'cillating current from the amplifiers. The

opposite end of the wire tape 8 may beconnacted to a swivel post 12 pivotally connected 8 to armature plate 1 by a in 13.

The lower member 0 the swivel post 12 may be provided with a semi-circular depression in its upper surface, a rod 14 being carried b theswivel post 12 and removably conthereto as by means of a machine screw 15. The end of the wire tape 8 may be held between the swivel-post 12 and the rod 14, said rod resting in the semi-circular concavity in the upper surface of the swivel ost 12 and held therein by means of the mac ine screw 15 the ta 8 being thus ippingl held between the ower jaw of theivel post 12 and the rod 14. A rounded electrical con nection may be made ween the swivel t 12 and a terminal post 23carried by the pa e 1 as by means of a coiled or flexible conductor.

wire 17.

Thebri 6 and 7 (made of non-conducting materia maintain the central portion of the tape 8 htly above the upper surfaces of the pole pieces 2 and 8, referabl the central portion of the tape lying a ut twothousandth of an inch above the upper surfaces of the pole pieces. Furthermore, the ribbon or tape 8 is positioned in such manner as to lie in alignment with the longitudinal axis of the rectangular slit formed in the pole pieces 2 and 8 so that when at rest one o 'tudinal edge of the ribbon 8 lies substanti y along the center line of the rectangular slit in the pole iece. Such positioning of the ribbon 8 is acilitated b means of side ards 18 and 19 carried y each of the ridges 6 and 7, such side guards 18 and 19 contacting with the side edges of the ribbon 8 and maintaining it approximately in the reuired position with regard to the aperture in he ole pieces.

e ribbon 8 is maintained under tension by means of a spring ,20 connected to one .end of the pivoted anchor member 12, the other end of the spring 20 being adjustable by means of machine screw 21, such machine screw 21 passing through the side walls 22 of the light valve and through the bus member 23 by means of which grounded contact is made with the armature plate 1.

One of the pole pieces, such as for exam is, the pole piece 3, may have its upper sur ace slightly milled down so as to receive a partial shield 24, such partial shield being carried by means of a non-ma etic supportin member 25 to which the s ield is attache as by means of screws 26. The member 25 may in turn be attached to the pole piece as by means of the screws 27 The upper surface of the shield 24 is preferably either in the same plane as or onethousandth of an inch above the upper surface of the pole piece 2.' The shield 24 partially covers the rectan lar slit in the pole ieces, thus permitting t e ribbon 8 to moduate the light passing through the remaining opening.

Positioned between the brid members 6 and 7 and the pole pieces 2 and are damping devices 30 and 31. Such damping devices may consist moral of tubular or cylindrical members provide with de ressions in their up r en such members ing suitably attac ed to the armature plate 1.

As shown in greater detail in Figure 3, the damping device may he provided with a depression 32 in its up er end, diametrically opplgsed apertures 33 being made in the side we These apertures 33 are preferably of a width exceedin the width of the ribbon 8. If, for example, t e ribbon 8 is six mills wide, the aperture 33 may be twice as wide. These damping devices 30 and 31 are then preferably filled with a suitable lubricant or nonvolatile viscous medium such as petroleum jelly, grease, hi hly refined non-volatile oil, a soap compoun or similar substance which does not evaporate, has a high surface tension, does not flow readily, and which, at the same time, exhibits plastic flow and 1s sumciently' plastic and e astic so as to absorb the vibrations of the ribbon 8 to a certain extent.

It has been found that ordinary grease, such as is employed for heavy hearings on automobiles, has the proper consistency for the urposes of this invention.

e apertures 33 formed in the upper end of the damping devices 80 and 81 are of suf- 1 ficient-depth so that the ribbon 8 is completely surrounded by the lubricant in the chem hers 82 of such damping devices.

It has been found that light valves con structed as above described and employing but a single ribbon or light modulating element are particularly eiiective in recording speech and music. Recordings produced by means of devices of this character are characterized by a brilliance of tone and distinctness, and for the fullness of tone aboveall.

Furthermore, it has been found that the ribbons 8 above the pole pieces do not sway along arcuate paths with the points of suspension on the bridge elements 6 and 7 as pivotal points, but instead, the ribbons merely vibrate in a flat plane. The tipping or angular position which the ribbons have formerly assumed when impulses of great amplitude pass through the ribbons, is completely obviated. There is no tendency for the ribbons to thus become jammed and contact with the pole pieces or become lodged in an angular position.

It is to be understood that it is not necessary to employ the shield 24 and the shield supporting element 25 unless it is desired to transform one of the valves of the prior art into 'a damped single element valve of the character embraced by this invention. The shield may be dispensed with wherever the rectangular slot or slit in the pole pieces does not exceed in width the width of the modulating ribbon and one edge of the slot is sufficiently straight and accurate. Furthermore, the invention isnot to be limited to the precise form of bridges or ribbon anchoring devices. The form of the damping devices may also vary. It is very essential, however, that some form of damper be positioned within the vibrating section of the ribbon as, for example, between thebridge members and the pole pieces.

Numerouschanges and modifications can be made in the arrangement of the elements and in their construction and form. All such I changes and modifications as come within the scope of the appended claims are embraced thereby.

I claim:

1. An improved light valve adapted to be activated by an oscillating current comprising an armature member, an aperture in said armature member, means for supportin a metallic tape over said armature mem er and over said aperture therein, a metallic tape suspended over said aperture and damping means carried by said armature member between said supporting means and aperture said damping means being adapted to hold a damping medium in contact with the metallic tape.

2. An improved light valve adapted to be activated by an oscil ating current comprismg in com 1 aperture in said armature member, mean for supporting a metallic tape over said armature member and over said aperture therein,

activated by an oscillating current comprising an armature member, pole pieces carried by said armature member, a slit in said armature member and pole pieces, bridge means for supporting a metallic tape over said pole pieces and. over the slit therein, a metallic tape suspended over said aperture, means for maintaining said tape under tension, and damping means carried by Said armature member betweensaid supporting means and pole pieces, said damping means being adapted to hold a damping medium in contact with the metallic tape.

4:. An improved light valve adapted to be activated by an oscillating current comprising in combination an armature plate, pole pieces carried by said armature plate, a slit in said pole pieces, bridge means carried by said armature plate for upporting a metallic tape over saidpole pieces and slit therein, a metallic, tape suspended over said pole pieces, a shield carried by one of said pole pieces and partially covering saidslit therein, means for maintaining said tape under' tension, and damping means carried by said armature plate between said bridge means and pole pieces, said damping means comprising a chamber, opposed apertures in the walls of said chamber adapted to loosely receive the metallic tape, and a damping medium carried in said chamber and surrounding said metallic tape.

of Dec., 1930.

7 'OLINDO O. CECCARINI.

Signed at Culver City, Calif., this 29th day nation an armature member, an 

